Thanks for that Godspeed. I'm going to be sending my drivelines to be rebuilt. One needs it (see above) the other will go along to be checked out, but I will leave the connecting driveline alone if good.
Today's adventure saw the replacing of the MHC switch and... no joy. Attempted to lower downriggers and nothing. I installed a pressure gauge at the test port and got no pressure. So, it is my PTO or pump. I imagine if it were my PTO that failed I would hear god awful grinding but it sounds smooth and I can feel flow by the spools. My best guess is pump impeller damage. The downriggers are without solenoids and should operate independent of the safety lockout system other than the the extension safety switch. Is that correct?
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Almost certain that the outriggers are not attached to anything electrically powered that would eliminate fluid passage.
By chance, have you had a look at the hydraulic filter? Stopped up maybe?
Tried using a yard stick (or similar length) to drop into the hydraulic tank?
• Checking for "goo" on the bottom or possibly water.
• Oil floats and water could (long stretch) have gone downhill to the pump and seized up the vanes in the pump maybe
• Partially closed valve on the bottom of the hydraulic tank - maybe? (FYI, The M1089 will stall the engine if the tank valve is completely closed)
Just a couple of things to look at for starters. When you turn on the PTO, you should hear a (hard to describe) moaning, whirring, sound. You should be able to clearly that sound pitch change. The Allison has to be in Neutral. to engage the hydraulics. PTO switch is pictured below (on the right).
Don't take any of this to sound like a "beat down"!
My goal was to give you some ideas to look at.
More to discuss...
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Another relatively cheap way to check the pump is to get a huge drain pan and disconnect the two hydraulic hoses from the pump.
Oil should be thin (10wt) and clear. Milky means water.
When the pump ports are open, attach another hose to the two ports that you opened.
Any hydraulic hose that is pressure rated @ 3000# or more.
THEN crank the truck again and engage the PTO. The sound coming from under the truck should be obviously different. You don't have hydraulic fluid other than the dribble in the pump so
don't run it more than just a few seconds. Sound (pitch) change should be obvious.
Maybe we can talk more. There are plenty of folks other than me who knows about these trucks and hydraulics. Don't hesitate. Heck, it could be as simple as a collapsed hydraulic suction hose. You might need a TRUSTWORTHY "Soldier B" to operate the truck while you are under or near the transmission to be able to hear better. These trucks do make a lot of racket when running. Stepped up to 1500/1800 rpm for pump operation it gets even louder.
